--with-libpng is incompatible with --without-zlib

[GoogleCodeExporter]

What steps will reproduce the problem?
1. run configure --with-libpng --without-zlib
2. make

What is the expected output? What do you see instead?

Linking fails:

bin/sh ../libtool --tag=CC   --mode=link x86_64-pc-linux-gnu-gcc  -march=native 
-O2 -pipe  -Wl,--as-needed -Wl,-O1 -Wl,--as-needed -Wl,--hash-style=gnu -o 
xtractprotos xtractprotos.o liblept.la 
libtool: link: x86_64-pc-linux-gnu-gcc -march=native -O2 -pipe -Wl,-O1 
-Wl,--hash-style=gnu -o .libs/xtractprotos xtractprotos.o  -Wl,--as-needed 
./.libs/liblept.so
./.libs/liblept.so: undefined reference to `readHeaderPng'
./.libs/liblept.so: undefined reference to `pixReadStreamPng'
./.libs/liblept.so: undefined reference to `pixReadMemPng'
./.libs/liblept.so: undefined reference to `pixWriteStreamPng'
./.libs/liblept.so: undefined reference to `pixWriteMemPng'
./.libs/liblept.so: undefined reference to `sreadHeaderPng'
collect2: ld returned 1 exit status

What version of the product are you using? On what operating system?

Gentoo Linux

Please provide any additional information below.

Maybe it has to do with libpng being dynamically linked to libz?

The corresponding Gentoo bug report is here:
https://bugs.gentoo.org/show_bug.cgi?id=454890

Original issue reported on code.google.com by feynma...@gmail.com on 14 Feb 2013 at 3:57

[GoogleCodeExporter]

It makes no sense to build using png without zlib, because png uses zlib for 
compression.

Original comment by dan.bloo...@gmail.com on 14 Feb 2013 at 5:50

• Changed state: WontFix

[GoogleCodeExporter]

I agree, I was just wondering wether configure should automatically enable zlib 
in case libpng is selected.  In any case, in Gentoo we can handle it with 
dependencies.

Original comment by feynma...@gmail.com on 14 Feb 2013 at 7:05